CHAPTER 2-144: SMOKE INHALATION

Smoke inhalation commonly occurs in fire victims and is associated with high morbidity and mortality. In addition to thermal injury, burning organic and inorganic materials can produce a very large number of different toxins, leading to chemical injury to the respiratory tract as well as systemic effects from absorption of poisons through the lungs. "Smoke bombs" do not release true smoke but can be hazardous because of irritant components, particularly zinc chloride.

Smoke is a complex mixture of gases, fumes, and suspended particles. Injury may result from the following:

1. Thermal damage to the airway and tracheobronchial passages.

2. Irritant gases, vapors, and fumes that can damage the upper and lower respiratory tract (Gases, Irritant). Many common irritant substances are produced by thermal breakdown and combustion, including acrolein, hydrogen chloride, phosgene, and nitrogen oxides.

3. Asphyxia due to consumption of oxygen by the fire and production of carbon dioxide and other gases.

4. Toxic systemic effects of inhaled carbon monoxide, cyanide, and other systemic poisons. Cyanide is a common product of combustion of plastics, wool, and many other natural and synthetic polymers.

The toxic dose varies depending on the intensity and duration of the exposure. Inhalation in a confined space with limited egress is typically associated with delivery of a greater toxic dose.

1. Thermal and irritant effects include singed nasal hairs, carbonaceous material in the nose and pharynx, cough, wheezing, and dyspnea. Stridor is an ominous finding that suggests imminent airway compromise due to swelling in and around the larynx. Pulmonary edema, pneumonitis, and adult respiratory distress syndrome (ARDS) may occur. Inhalation of steam is strongly associated with deep thermal injury but is not complicated by systemic toxicity.

2. Asphyxia and systemic intoxicants may cause dizziness, confusion, syncope, seizures, and coma. In addition, carbon monoxide poisoning, cyanide poisoning, and methemoglobinemia have been documented in victims of smoke inhalation.

Should be suspected in any patient brought from a fire, especially with facial burns, singed nasal hairs, carbonaceous deposits in the upper airways or in the sputum, or dyspnea.

1. Specific levels. Carboxyhemoglobin and methemoglobin levels can be measured with co-oximetry. Unfortunately, cyanide levels are not readily available with short turnaround times; thus, the diagnosis is usually based on clinical findings.

2. Other useful laboratory studies include arterial blood gases or oximetry, chest radiography, spirometry, or peak expiratory flow measurement. Arterial blood gases, pulse oximetry, and chest radiograph may reveal early evidence of chemical pneumonitis or pulmonary edema. However, arterial blood gases and conventional pulse oximetry are not reliable in patients with carbon monoxide poisoning or methemoglobinemia. (A newer pulse co-oximeter is capable of detecting carboxyhemoglobin and methemoglobin.)

1. Emergency and supportive measures

   1. Immediately assess the airway; hoarseness or stridor suggests laryngeal edema, which may necessitate direct laryngoscopy and endotracheal intubation if sufficient swelling is present. Assist ventilation if necessary (Breathing).

   2. Administer high-flow supplemental oxygen by tight-fitting non-rebreather mask.

   3. Treat bronchospasm with aerosolized bronchodilators.

   4. Treat pulmonary edema if it occurs.

2. Specific drugs and antidotes

   1. Carbon monoxide poisoning. Provide 100% oxygen by mask or endotracheal tube. Consider hyperbaric oxygen.

   2. Cyanide poisoning. Empiric antidotal therapy with hydroxocobalamin is recommended for patients with altered mental status, hypotension, or acidosis. If hydroxocobalamin is not available, sodium thiosulfate from the conventional cyanide antidote kit may also be effective. Note: Use of sodium nitrite is discouraged because it may cause hypotension and aggravate methemoglobinemia.

   3. Treat methemoglobinemia with methylene blue.

3. Decontamination. Once the victim is removed from the smoke environment, further decontamination is not needed.

4. Enhanced elimination. Administer 100% oxygen and consider hyperbaric oxygen for carbon monoxide poisoning.